Automatic control system for hot-strip mill and the like

ABSTRACT

In a cooling process for a hot-strip mill wherein cooling water is sprinkled on a strip from a plurality of spray banks thereby to cool the strip and to control the winding temperature thereof, the temperature of the strip at the inlet of the process is detected, the initial value of a function prescribing a desired temperature falling rate is calculated from the detected value, and it is applied to a first analog shift register. At every movement of the strip by the unit distance, the moving period of time is detected to be applied to the respective elements of a second analog shift register. Simultaneously therewith, shift pulses are applied to both the registers. The respective elements of both the registers are subjected to sampling to calculate a predetermined cooling power by a calculating device. The calculated value is distributed to the respective driving devices, to thereby manipulate the spray banks.

United States Patent Nara Oct. 9, 1973 1 AUTOMATIC CONTROL SYSTEM FOR HOT-STRIP MILL AND THE LIKE Akinao Nara, Kodaira, Japan Hitachi, Ltd., Tokyo, Japan Dec. 16, 1971 Inventor:

Assignee:

Filed:

Appl. No.:

[30] Foreign Application Priority Data Dec. 16, 1970 Japan 45/111801 U.S. C1 235/151.1, 148/143, 148/153, 235/150.1 Int. Cl. G05b l1/01' Field of Search 148/143, 153; 235/151.1

References Cited UNITED STATES PATENTS 6/1962 Chope 235/l5l.l X 11/1969 .Adams 164/4 OTHER PUBLICATIONS Controlling a Complete l-lot Strip Mill by Brower, Control Engineering, pp. 57-63, Oct. 1963.

Primary Examiner-Eugene G. Botz Attorney-Craig, Antonelli & Hill [5 7] ABSTRACT In a cooling process for a hot-strip mill wherein cooling water is sprinkled on a strip from a plurality of spray banks thereby to cool the strip and to control the winding temperature thereof, the temperature of the strip at the inlet of the process is detected, the initial value of a function prescribing a desired temperature falling rate is calculated from the detected value, and it is applied to a first analog shift register.

16 Claims, 14 Drawing Figures PROCESS l. I i l G MANIPULATIN i MEANS SPEED DRIVING DRIVING DET d'E i DEVICE DEVICE l2 I5 4, l NH FUNCTION ANALOG MEMORY GEN A l l J, J, l 9 ISAMPLING DEVIGE O 7 CALCULATING f f DEVICE ALOG SHIFT REGlST- ER lllll lll e I4 I T LSAMPLING oEvIc TIMER \8 PATENTEUUBI 9191a SHEET 10F e FIG. I ,I

, PROCESS L I I I MANIPULATING S A "1 MEANS Q VALUE DRIVING H DRIVING DET DEVICE DEVICE 42 I5 4 I VH FUNCTION ANALOG MEMORY GEN A A I I J A L 9 SAMPLING DEVIGEJ 7 CALCULATING ff ff f?? DEVICE SP AAA-T REGIST- ER LAkiMs I4\I l J T LSAMPLING DEVICE TIMER \8 FIG. 3

l6 AX l8 X -INTEGRATQR COMPARATOR SP I 0N- DELAY OFF-DELAY I ELEMENT ELEMENT I 22 'INTEeRAT0R E0 INVENTOR AKINAO NARA v BY A BMLMIw-IE m ATTORNEYS PATENTED 9 I973 SHEET am 6 FIG 6 39 /4O WINDING TEMPERATURE SEE E MULTIPLIER -|o DETECTOR mm {I+B(e)} Fl G 7 INVENTOR Am NA 0 NAR ATTORNEYS SHEET 5 BF 6 PATENTEBUCT 91975 TEMPERATURE DETECTOR Wm WWW FIG l0 I l I l I I l I COMPARATOR-J i?w qqu FUNCTION GENERATOR ADDER INVENTOR AKINAO NARA QMtoM/Q/QA' b-H-L Z ATTORNEY5 BY Cfoulca AUTOMATIC CONTROL SYSTEM FOR HOT-STRIP MILL AND THE LIKE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to automatic control systems, and more particularly to a novel automatic control system in which a distributed product or object as in a hot-strip mill, a continuous casting process, etc., is controlled with a distributed, manipulated variables.

2. Description of the Prior Art In the case where a distributed product or object, e.g., the winding temperature of a strip in a hot-strip mill, is controlled, cooling spray banks are arranged so as to be distributed along the strip mill. Heretofore, however, even when such distributed manipulating means has been provided, a control system utilizing it effectively and appropriately has not been adopted. In spite of the presence of the distributed product or object and manipulating means, they have been regarded as centralized ones and a feed forward control system with conventional centralized manipulating means has been employed. Alternatively, there has been employed a feed forward control system in which the construction and the manipulating method of the manipulating means are rationalized to some extent. Included among examples of the adoption of the former control system is one wherein the spray bank for pre-setting is arranged on the mill side, while the spray bank for control is arranged on the winding side, whereby approximately the necessarypooling power is obtained at the pre-setting spray spray bank, while in the case where the necessary cooling power is insufficient with only the manipulation of the presetting spray bank, the cooling power is compensated at the control spray bank. Herein, large-sized ON-OFF valves are used for the pre-setting spray bank, while small-sized ON-OFF valves for the control spray bank.

As an example of the adoption of the latter control system, there is one using continuous manipulating valves for the aforesaid control spray bank. With either system, however, a winding-temperature control error sometimes becomes large on account of fluctuations in the winding speed, mill-outlet temperature or reference winding temperature. Furthermore, even if the winding temperature may be controlled so as to follow a reference value, the temperature falling rates at various parts of the strip differ and, disadvantageously, the metallurgic quality of the strip does not become uniform.

' SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic control system which, in order to eliminate such disadvantages, controls a distributed product or object with distributed, manipulated variables.

Another object of the present invention is to provide an automatic control system which may satisfy not only the aforesaid control of the winding temperature, but also a high level of control such as the control of a temperature falling ratio or rate.

Still another object of the present invention is to positively utilize the distributing character of manipulating means, to thereby enhance the quality of products and to simplify the control method thereof.

In order to accomplish the above-mentioned various objects, the present invention is characterized in that,

in a process having a product or object distributed in the first, second or third dimension of space, the whole distribution of manipulated variables exerted upon the product or object is considered as one pattern, the manipulated variables are distributed so as to coincide with a standard pattern of the manipulated-variable distribution as is required for a desired product quality and the standard condition of the process, to thereby be fed to the product or object, and the standard pattern is altered in response to changes in the conditions of the process, etc.,

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the basic construction of the present invention;

FIG. 2 is a, schematic diagram showing an embodiment of the present invention;

FIGS. 3 and 4 are schematic diagrams each showing a practical embodiment of the construction of the es sential portions of the embodiment in FIG. 3;

FIGS. Sa-Se show curve diagrams which illustrate a variety of standard distribution patterns of manipulated variables;

FIG. 6 is a block diagram showing the construction of a feedback control system added to the above embodiment;

FIG. 7 is a schematic diagram showing a temperature model of a slab;

FIGS. 8 and 9 are diagrams showing another embodiment of the present invention; and

FIG. 10 is a schematic diagram showing a practical embodiment of the construction of the essential portions of the embodiment in FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be hereinbelow described in more detail with reference to the preferred embodiments. As previously stated, even if provided with distributed manipulating means, the prior-art feed forward control system does not utilize it effectively. In the prior-art processes having a distributed product or object, the distributed manipulating 'means is not positively adopted, but rather, it cannot avoid being employed on account of physical restrictions in many cases. For example, in the aforesaid case of the winding-temperature control for a hot-strip mill, there exists the situation that, since it is difficult to cool the strip to the reference temperature with only the spray bank disposed at one place, the spray banks are distributed and arranged.

The present invention has successfully studied the merits which the distributed manipulating means has for the aforesaid process. As a result, in order to positively utilize the distributing character of the manipulating means, the invention provides a feed forward control system in which the whole distribution of manipulated variables exerted upon the controlled system by such manipulating means is dealt with as one pattern, the distribution pattern of the manipulated variables is made so as to satisfy a condition of the process as enhances the product quality (for example, a standard pattern of the manipulated-variable distribution as provides the reference winding temperature and the desired temperature-falling rate), and the condition is altered in response to a change in the state of the process.

In a product having a distributed controlled variable, distributed in conformity with the moving speed of the product, so that it may be considered as one control aim to control changes-versus-time of such a distributed, controlled variable. For example, a fixed period of time is required in order to cool the hot strip to a reference winding temperature and, hence, the control of the falling rate of the strip temperature may be regarded as such a control aim. Accordingly, if the temperature falling rate may be controlled so as to coincide with a function capable of enhancing the product quality, products of higher quality than in the prior art may be obtained.

In order to control the distributed, controlled variable so as not only to coincide with the reference value but also to have its changes versus time made the pattern of the desired function, manipulated variables exerted upon the product or object may be distributed so as to make the distribution pattern a predetermined one. The fact that the product or object is spatially distributed, and insofar as the moving speed thereof is finite, causing the changes-versus-time in the controlled variable at various points of the controlled system to coincide with a desired pattern, is equivalent to cause the spatial distribution of the controlled variable to coincide with a predetermined pattern. For this reason, a distributed manipulating means is used in the present invention. Thus, the distributed, manipulated variables in accordance with the desired pattern may be imparted to the object or product. In such a sense, the present invention may be defined as a system effecting a pattern-like control with the distributed manipulating means. The distributed, manipulated variable density (manipulated variable per unit length) fed from the re spective positions of the distributed manipulating means is changed in conformity with the lapse of time corresponding to the movement of the product or object, and is thereby controlled so that the distribution pattern of the manipulated variable may coincide with a function representing the desired pattern. That is to say, the manipulated variables imparted to the product or object with its movement according to a specific state are determined by changes-versus-time in the distributed manipulated-variable densities given at the respective positions of' the distributed manipulating means. In this manner, the patterndike control with the distributed manipulating means is suited to the feed forward control of the process having the distributed product or object.

FIG. 1 shows the basic construction of the aforesaid system of the present invention. In the figure, numeral 1 designates a process, 2 a distributed product or object which moves between the input and output of the process, 3 an initial-value detector for a controlled variable, 4 a function generator which generates a function prescribing changes-versus-time in the controlled variable, 5 and 6 analog shift registers, 7 and 8 sampling devices for taking out outputs from the respective memory components constituting the registers, 9 a calculating device for the density of manipulated variables, 10 a distributor, 11 an analog memory for storing the manipulated-variable density distributed by the distributor, 12 a driving device, and 13 a manipulating means distributed and arranged along the process 1 and consisting of a plurality of manipulators. The analog shift register has a plurality of analog storage elements, e.g., analog core elements, connected in series, and has the function of successively shifting an input analog quantity to the next element by means of shift pulses SP simultaneously applied to the respective elements. Analog shift registers per se, are well known. The shift pulses are produced by a timer 14 every time the object or product 2 is moved by a unit distance (the disposed interval between each manipulator). To the timer 14, there is applied an output signal V(t) from a speed detector 15 of the product or object 2. Further, at every movement of the product or object 2 by the unit distance, the timer 14 applies simultaneously to the respective analog storage elements of the analog register 6 a timing signal which represents the moving time T of the controlled system.

The functions prescribing the changes-versus-time in the controlled variable are previously evaluated experimentally and theoretically, and are preset in the function generator 4. The function generator 4 generates a functional output in response to the initial value of the controlled variable detected by the detector 3, and applies it to the first element of the analog shift register 5. The calculating device 9 calculates a required manipulated-variable density from the functional output and the moving time of the product or object 2. Herein, since the manipulated-variable density is used to cause the change-versus-time in the controlled variable to coincide with a desired pattern as has been previously stated, it should be distributed in correspondance with the respective spatial positions of the product or object 2. For this reason, at every movement of the product or object 2 by a unit distance, the functional output and the moving time are shifted into the analog shift registers 5 and 6 by the shift pulses SP, and they are taken out from the respective elements of the respective registers by the sampling devices 7 and 8.

On the other hand, the distributor l0 distributes the mainpulated-variable density, calculated by the calculating device 9, to the respective manipulators of the manipulating means 13 through the analog memory 11 and the driving device 12 in synchronism with the sampling devices. Herein, the operating speeds of the sampling devices and the distributor are made sufficiently high in comparison with the shift period in the registers (the moving speed of the product or object 2), so that all the sampling and distributing operations may be completed before the contents of the registers are shifted.

In this manner, the manipulated-variable densities required at the respective spatial positions of the product or object 2 may be obtained, and they are successively fed from the respective manipulators with the movement of the product or object 2. Thus, the manipulated variables are fed to the product or object 2 in such a manner as to realize a predetermined standard pattern in conformity with the movement of the product or object and, hence, the changes-versus-time in the controlled variable may be controlled so as to coincide with the pattern. While the standard pattern is determined dependent upon the pattern of the changesversus-time in the controlled variable as is required to enhance the quality of a product and on the standard condition of the process, it may of course be suitably altered.

Description will now be made of a cooling and winding process in a hot-strip mill to which the construction of the present invention as described above is applied. This process has a product or object of a onedimensional distribution (strip), and the metallurgic quality of the strip is influenced by the temperature falling rate (changes-versus-time in the controlled variable) and its pattern when the strip is cooled to a reference winding temperature until it leads to an outlet of 5 sirable that the temperature falling rate JI(t)/dt becomes a function f [T(t)] of only the temperature T(t). That is,

where T(t) represents the temperature of one point on the strip, t a lapsing period of time of the strip movement from the inlet of the process to this point, and f [T(t)] a function prescribing the pattern of the temperature falling rate at the above-mentioned point, which is previously evaluated from experimental and theoretical studies. Accordingly, the temperature T(t) as the controlled variable should be so controlled as to become:

where T(()) represents the strip temperature at the inlet (the initial value).

Assuming the cooling power of each spray to be m(x, t) and the thickness of the strip to be h, the actual temperature falling rate of the strip becomes:

where x represents a distance from the inlet to the particular spray. Since, in order to bring the actual temperature falling rate into coincidence with a desired pattern, equation (3) may be made equal to equation (1), the relation between the strip temperature and the spray cooling power to be manipulated is evaluated as the following expression:

mu. 0 h rmo /m) However, for T(t) T (reference winding temperature) the cooling power is determined as in the above expression, and m(x, t) is equal to 0 if T(t) T FIG. 2 shows an embodiment of the cooling and winding process according to the system of the present invention. In the figure, the same symbols as in FIG. 1 have the same functions. More specifically, the detector 3 detects the initial temperature T(O), and transmits it to the function generator 4. The function f [T(t)] is kept set in the function generator 4, and the functional output f [T(O)] thereof is applied to the first element of the analog shift register 5. The timer 14 transmits the shift pulses SP to the analog shift registers 5 and 6 in synchronism with the movement of the strip 2, and therewith, it applies the timing signal T to the respective elements of the register 6 at each movement of the strip 2 by the unit distance (the spray interval Ax). Ac-

cordingly, in the n-th element of the analog shift register 6, a period of time t elapses until the point on the strip arrives at the n-th spray after passing through the inlet.

where t,, represents the lapsing time having been accumulatedin the element immediately before the n-th I one, while ida? the moving time T for the unit distance.

FIG. 3 shows a practical embodiment of the timer 14. Referring to the figure, numerals l6 and 17 designate integrators, 18 a comparator, 19 an OFF delay element, 20 an ON delay element, and 21 and 22 switches. To the input of the integrator 16, a speed detection signal V(t) is applied from the speed detector 15 for the strip. A voltage corresponding to the unit distance Ax is applied to one of the inputs of the comparator 18, while an output signal of the integrator 16 is applied to the other input. When an output signal is produced from the comparator 18, it is transmitted to the analog shift registers. Simultaneously therewith, it is applied through the OFF delay element 19 and the ON delay element 20 to the reset switches 21 and 22, to turn them ON to ground the integrators 16 and 17. The OFF delay element 19 has the function of delaying an of operation by a certain period of time 1', while the ON delay element 20 has the function of delaying an on operation by a certain period of time 1'. A variety of types of these elements are commercially available.

Withthe construction as described above, the shift pulse SP having a width r is produced'as the output signal of the comparator 18 for every movement of the strip 2 by a unit distance Ax, while the integrator 17 is grounded each time. Accordingly, if a certain fixed voltage E, isapplied to the input of the integrator 17, a voltage E proportional to the moving time T for the unit distance Ax is obtained at the output thereof. The voltages B are accumulated in the respective elements of theanalog shift register 6.

FIG. 4 illustrates a practical embodiment of the calculating device 9. In the figure, numeral 23 indicates an exponential-function generator, 24 and 25 multipliers, 26 the same function generator as function generator 4, 27 an operational amplifier, 29 a comparator, and 30 a switch opened and closed by the outputs of the comparator 29. The exponential-function generator 23 produces an exponential function e"" in response to the time lapse 1,, taken from the analog shift register 6 by the sampling device 8. The aforesaid functional output f [T(O)] stored in the element of the analog shift register 5 is taken out by the sampling device 7, to be applied to one of the inputs of the multiplier 24, while the output of the exponential generator is applied to the hQ Li Bfl -A a r921! aml t rlxi ssis fl 1 e"" =flT(t,,) is obtained at the output of the miiltiplier 24. Since the function generator 26 may be regarded as a feedback impedance for the operational amplifier 27, these constitute an inverse-function generator as is well known, and an inverse-function output 7 T(t,,) =f [f(T() )e""] is obtained at the output of amplifier 27.

The multiplying signal is applied to one of the inputs of the multiplier 25, while a thickness output from a detector 32 shown in FIG. 2, for the thickness h of the strip 2 is applied to the other input. The divider 28 divides the output h fIT( t of the multiplier 25 by the inverse-function output T0,), to calculate a predetermined spray cooling power h'flT(t,,)]/T(t,,) =m(x, t,,) and applies it to an input terminal 33 of the switch 30.

On the other hand, the inverse-function output T( t,,) is also applied to one of the inputs of the comparator 29, and is compared with the reference winding temperature T applied to the other terminal 31. As a result, if T(t,,) T,,,, the switch 30 contacts the input terminal 33, and hence, the spray cooling power m(x, t,,) is distributed to a predetermined element of the analog memory 11 by means of the distributor 10. In contrast, if T( 1,.) T the switch 30 contacts grounded terminal 34, and hence, m(x, t,,) becomes zero.

The respective elements of the analog memory 1 l are connected to the driving device 12 comprising a servoamplifier, etc., continuous manipulating valves 35 are continuously manipulated by said device, and cooling water supplied from a pump 36 is sprayed onto the strip by a plurality of sprays 37. In this case, the quantity of the cooling water sprayed in the strip corresponds to the cooling power m(x, t Moreover, as previously stated, the cooling water is sprayed from the sprays corresponding to the respective spatial positions of the strip, with the movement of the strip. Thus, the respective parts of the strip are cooled to the reference winding temperature at a temperature falling rate conform ing to a desired pattern.

FIGS. a-5e illustrate standard distribution patterns of the aforesaid spray cooling power. The quantity of the cooling water sprayed from the respective sprays 37 distributed and arranged from the inlet to the outlet, is controlled in the manner above described and so as to conform to one of the patterns. Assuming that the standard distribution pattern is represented as in FIG. 5a for, e.g., h, V(t), T(O) and T then that for 2h, V(t), T(O) and T is depicted as in FIG. 5b, that for h, l.5V(t), T(O) and T as in FIG. 50, that for h, V(t), T(O) AT (AT 0) and T as in FIG. 5d, and that for h, V(t), T(O) and T AT (AT 0) as in FIG. 5e more specifically, that standard distribution pattern of the manipulated variable corresponding to the standard condition of the process which is illustrated in FIG. 5a, has its values on the axis of ordinates multiplied by 2 in FIG. 5b, has its values on the axis of abscissas multiplied by 1.5 in FIG. 5c, is subjected to a rightward movement by AL in FIG. 5d, and has its values on the axis of abscissas shortened by AL in FIG. 5e. In this way, the standard distribution pattern is altered in correspondence with changes in the parameters, and the manipulated variables are calculated in conformity with the altered pattern. As described above, the alteration of the standard distribution pattern is extremely easy, and said pattern may quickly correspond to the changes in the parameters.

When, in the foregoing embodiment, not only the feed forward control but also the feedback control is conducted, and a more accurate temperature control becomes possible. To this end, a winding-temperature detector 38, a correcting device 39 and a multiplier 40 are employed as shown, by way of example, in FIG. 6.

The correcting device 39 generates a correcting signal E in response to an error or deviation e between a wind ing temperature T, detected by the detector 38 (the final controlled variable) and the reference temperature T The correcting signal E is expressed by E l B(e), where B(e) is a function representing the correcting ratio of the cooling power as is required for the error e and being previously set, and 8(0) 0. The correcting signal E and the cooling power m(.x, t,,) calculated by the calculating device 9 are subject to multiplication in the multiplier 40, and a resulting corrected cooling power is fed to the distributor 10.

There will now be described an embodimentin which the construction of the present invention is applied to a continuous casting process as a process having a controlled object or system of three-dimensional distribution.

The spray cooling process for a slab in the continuous casting has similar characteristics to those in the hot strip. However, the product or object in the former case is the temperature distribution of three dimensions within the slab, and is not so simple as that for temperature control at points in the strip. More specifically, for the hot strip, since the temperature difference between the edge parts and the inner part of the cross section of a strip is negligible, the surface temperature may be regarded as the controlled variable. In contrast, for the slab, since the temperature difference is large, the temperature distribution pattern in the cross section of the slab should be considered as the controlled variable. As a temperature model representing such pattern, there may be considered a set of rectangular parallelepipeds each having, as shown in FIG. 7, the dimensions of AL X A/P X B/P (where AL represents the spray interval in the advancing direction of the slab, A the longitudinal length of a cross section of the slab, B the lateral length of the slab cross section, and P apositive integer). In the rectangular parallelpipeds, a mathematical expression model concerning the temperature T,,( of the j-th cube at the i-th one of the slab cross sections cut at the intervals of AL, may be represented by the following formulae:

m( Tim.) v

Herein, t, represents a time lapse with respect to the time at which the i-th slab cross section has passed through a mold outlet, A the heat conductivity of the inner part of the slab, T ,..(t the temperature of a cube adjoining in the n i direction to a cube at the i-th slab cross section, and the character g1 one of indices indicating directions, which are determined as l, 2, 6, respectively, for the upward, downward, leftward, rightward, frontward and backward directions. X takes the value of 0 at the surface of the slab and the value of l at the inner part of the slab, with respect to the m direction of the j-th cube at the i-th slab cross section. X,,,,, takes the inversed value of X,,,,,. C represents the specific heat of the slab, while p the density of the slab. AL is equal to A/P at m =1 or 2, to B]? at m=3 or 4 and to AL at m=5 or 6. The symbol k,, (L,) represents the cooling power density of the spray as is exerted, when the i-th slab cross section has arrived at L, from the mold outlet along the slab, upon the slab at said cross section from the m direction. V(t,) indicates a speed when the i-th cross section of the slab has experienced the lapse of the above-mentioned period of time t,.

It is now assumed that, as in the foregoing case of the strip, the temperature falling rate d1r,(t,)/dt is controlled so as to be a function fl1r,(t,)] of only the temperature as in the following equation:

where 1r, indicates the temperature distribution pattern at the i-th slab cross section, and represents T,,(t,), j l, 6 in the above equation (6).

In this case, the control conditions given by equation (8) may not be independently selected as is possible in the previous equation (2), and should be selected from among those which may be realized by the formulae (6) and (7).

Eqaution (6) is solved by putting thereinto V(t) and the initial value 'n',( At), At 0 of 1r,(t,) and replacing k,,,(L,) with k,,,,(t,), and thus, k,,,,(t,) with which the most preferably relation between 1r,(t,) and d1r,(t,)/dt, is obtained is previously evaluated. However, k,,,,(t,) shall be re-evaluated for different materials and/or configurations of the slab, and it shall be equal to 0 after T,,,,(t,) has coincided with a reference temperature T,,,,,. The reason why the initial value is not 1r,(0) but 1r,( Al), is that even when a relation as in expression (9) is brought about in the process of the control, the desired manipulated-variable distribution k,,,(L,) may be evaluated from the above-mentioned k,,,,(t,) in expression (1 l where T,,,,(t,) is T,,,,(t,) which is evaluated by substituting k,,,,(t,) into k,,,(L,) in equation (6). The above T,,,,(t,) indicates the temperature of a specified surface part among T,,(t,) at point of the slab, while T,,,,(0) represents the detected temperature value of the surface part at t, 0.

Since At, in expression (9) may be found from expression 10), the manipulated-variable distribution k,,,(L,) is calculated on the basis of it.

M- Am T,,,,(0), M A;

Herein, k,,,(L,) should be evaluated on various points of the slab within the range L, 0-L,, (the distance from the mold outlet to the temperature detecting point of the cooling process). Whether or not L, falls within the range is discriminated by the above-mentioned expression (7).

FIGS. 8 and 9 illustrate an embodiment of a spray cooling process for a slab in a continuous casting process which adopts the aforesaid feed forward control system. Referring to the figures, a mold device 41 has the function of injecting smelted steel into a mold, subsequently water-cooling the mold to solidify the contact area between it and the smelted steel, and continuously drawing out a slab. The slab drawn out is introduced into a cooling process similar to that in the case of the strip.

In the cooling process, a temperature detector 42 detects the surface temperature T,,,,(0) of the specified part of the slab, and feeds it to a function generator 43. The function generator 43 has previously set therein a function based on expression (10), and generates At', corresponding to the temperature T,,,,(0). Analog shift registers 44 and 45, a timer 46 and a speed detector 61 have the same functions as in the case of the embodiment in. FIG. 4. v

A calculating device 47 serves to calculate the manipulated-variable distribution k,,,(L,) on the basis of expression (1 l and an example of construction thereof is shown in FIG. 10. In the figure, numeral designates an adder, while 51 is a function generator; Ar, and t, taken out from the analog shift registers 44 and 45 by means of sampling devices 48 and 49 are fed to the adder 50, and therewith, an added output t, Al, is applied to a function generator 51. The function generator 51 has previously set therein a function based on expression (ll), and generates the manipulated variable k,,,(L,) corresponding to the added output. Cooling water responsive to the manipulated variables is subsequently sprayed onto the slab, and means therefor relies on a construction similar to that in the embodiment in FIG. 4. More specifically, numeral 52 represents a comparator, 53 a switch opened and closed by the comparator, 54 a distributor, 55 an analog memory, 56 a driving device, 57 a pump, 58 a continuous manipulation valve, 59 a spray, and 60 a pinch roll. In order to carry out the feedback control for the purpose of enhancing the precision of the control, a construction similar to that in the case shown in FIG. 6 may be employed.

Since the respective dividers from the function generator 51 to the analog register 55 are required for each of the four faces of the slab, four sets of them should be installed in parallel.

As described above, according to the present invention, a rational and effective feed forward control capable of satisfying even a high level of control such as a temperature falling rate may be realized, e.g., in a cooling process for a hot-strip mill having a distributed product or object. Thus, remarkable effects such as the enhancement of the quality of products are exhibited.

What I claim is:

1. An automatic control system for a distributed, controlled object which moves between an input and an output of a process, comprising:

an initial-value detector for a controlled variable of the controlled object; a function generator to which the initial-value of the controlled variable from said detector is applied for generating a function prescribing changes-versus-time in said controlled variable;

a first analog shift register for storing a functional output of said function generator;

a second analog shift register for accumulating a moving period of time of said controlled system at every movement thereof by a unit distance;

a timer for generating at every movement of said controlled system a shift signal for successively shifting the contents of each analog storage element of both said registers to the adjoining element and a signal representing said moving period of time;

sampling devices for taking out the contents of said each element of both said registers;

a device for calculating a manipulated-variable density from said functional output and the accumulated period of time taken out by said sampling devices; an analog memory; a distributor for successively distributing said manipulated-variable density to said each analog storage element of said analog memory in synchronism with said sampling devices; and

manipulating means for successively supplying said manipulated-variable density from said memory to said controlled object, said manipulating means having a plurality of manipulators which are arranged in a manner to be distributed along said controlled object.

2. An automatic control system according to claim 1, further comprising a detector for detecting a final value of said controlled variable;

means to calculate a correcting ratio for said manipulated-variable density in conformity with a deviation between said final value and a reference value; means to multiply said correcting ratio by said manipulated-variable density; and

means to supply the multiplying output from said multiplying means to said distributor;

3. An automatic control system for controlling the characteristics of an object during a process performed on said object, through which said object passes through a processing means, comprising:

first means, coupled to said object at its input to said processing means, for detecting a first parameter to be employed as a control variable for controlling said characteristics;

second means, responsive to said first means, for gencrating a function of said control variable with respect to time and producing a signal representative of said function;

third means, responsive to the rate of the entry of said object into said processing means, for generating a first timing signal representative of each increment of movement of said object into said processing means and a second timing signal representative of the time period which has elapsed from the initial entry of said object into said processing means;

fourth means, responsive to said function representative signal and said first timing signal, for sequentially storing portions of said function signal as they are produced and as said object moves through said processing means;

fifth means, resonsive to said first and second timing I signals, for storing said second timing signals and for generating a signal representative of a lapse of time from the initial movement of said object into said processing means;

sixth means, responsive to the output of said fourth and fifth means, for sampling the outputs thereof for each of said increments of movement of said object through said processing means;

seventh means, responsive to said sixth means, for

generating a characteristic control signal, for each of said sample outputs of said fourth and fifth means, said characteristic control signal being dependent upon the changes in said control variable; and

eighth means, responsive to the characteristic control signal output of said seventh means, for applying at least one input to said object passing through said processing means, so as to control the characteristics of said object in accordance with said characteristic control signal.

4. A system according to claim 3, wherein said eighth means comprises an anlog memory to which the output of said seventh means is coupled, a plurality of distributors for receiving the output of said memory and generating a plurality of manipulating signals; and

a plurality of manipulating means, for receiving said manipulating signals and controlling the characteristics of said object in response thereto.

5. A system according to claim 4, wherein said fourth and fifth means each comprises a shift register for shifting the inputs thereto in response to saidfirst timing signal.

6. A system according to claim 5, further including ninth means, coupled to said object, for detecting a second parameter to be employed as a correcting variable, and responsive to the output of said seventh means, for correcting the output thereof with respect to said second parameter and coupling said corrected output to said eighth means.

7. A system according to claim 4, wherein said seventh means comprises a predetermined function generator, receiving the output of said fifth means, for generating a function of the output thereof, a first multiplier for multiplying the output of said predetermined function generator by the output of said fourth means, a second multiplier, for multiplying the output of said first multiplier by a signal representative of a prescribed parameter of said object passing through said processing means, an operational amplifier connected to the output of said first multiplier and a function generator for feeding back the output of said operational amplifier to the input thereof, a divider circuit for dividing the output of said second multiplier by the output of said operational amplifier, a comparator circuit, for comparing the output of said operational amplifier with a threshold level, and a switching circuit, for supplying the output of said divider circuit to said eighth means in response to the output of said comparator circuit.

8. A system according to claim 4, wherein said third means comprises a first integrator circuit for integrating a signal representative of the rate of entry of said object into said processing means, a comparator circuit for comparing the output of said first integrator with a preset rate level and generating said first timing signal as a result of said comparison, a series delay circuit for delaying said first timing signal, a second integrator, responsive to an input voltage, for integrating said voltage in accordance with the output of series delay circuit.

9. A system according to claim 8, wherein said seventh means comprises a predetermined function generator, receiving the output of said fifth means, for generating a function of the output thereof, a first multiplier for multiplying the output of said predetermined function generator by the output of said fourth means, a second multiplier, for multiplying the output of said first multiplier by a signal representative of a prescribed parameter of said object passing through said processing means, an operational amplifier connected to the output of said first multiplier and a function generator for feeding back the output of said operational amplifier to the input thereof, a divider circuit for dividing the output of said second mulitplier by the output of said operational amplifier, a comparator circuit, for comparing the output of said operational amplifier with a threshold level, and a switching circuit, for supplying the output of said divider circuit to said eighth means in response to the output of said comparator circuit.

10. A system according to claim 9, further including ninth means, coupled to said object, for detecting a second parameter to be employed as a correcting variable, and responsive to the output of said seventh means, for correcting the output thereof with respect to said second parameter and coupling said corrected output to said eighth means.

11. A system according to claim 10, wherein said fourth and fifth means each comprises a shift register for shifting the inputs thereto in response to said first timing signal and wherein said object comprises a slab to be cooled during a continuous casting process carried out by said processing means on said slab, said first parameter corresponds to the temperature of said slab, said prescribed parameter corresponds to the thickness of said slab, said threshold level corresponds to a threshold temperature level, said predetermined function-comprises an exponential function, and said manipulating means comprises a plurality of cooling elements for cooling said slab.

12. A system according to claim 11, wherein said ninth means comprises a winding temperature detector, for generating a signal representative of the winding temperature for said slab, a correcting device responsive to the winding temperature signal and to said threshold temperature for generating an error signal representative of the difference therebetween, and a multiplier for multiplying said error signal by the output of said seventh means so as to provide a corrected characteristic control signal to said manipulating means. 7

13. A system according to claim 12, wherein said cooling means comprises a plurality of spray nozzles distributed along said object in accordance with spaces of incremental movement thereof through said processing means.

14. A system according to claim 4, wherein said fourth and fifth means comprise a plurality of parallelarranged shift registers, corresponding to the number of surfaces of said object to be manipulated, and wherein said seventh means comprises an adder circuit for adding the incremental outputs of said shift registers and a function generator for generating a control output in response to the sum of said incremental outputs of said shift registers in accordance with a prescribed function, a comparator circuit for comparing the output of said function generator with a threshold level, and a switching circuit for supplying the output of said function generator to said eighth means in response to the output of said comparator.

15. A system according to claim 14, wherein said third means comprises a first integrator circuit for integrating a signal representative of the rate of entry of said object into said processing means, a comparator circuit for comparing the output of said first integrator with a preset rate level and generating said first timing signal as a result of said comparison, a series delay circuit for delaying said first timing signal, a second integrator, responsive to an input voltage, for integrating said voltage in accordance with the output of series delay circuit.

16. A system according to claim 15, further including ninth means, coupled to said object, for detecting a second parameter to be employed as a correcting variable, and responsive to the output of said seventh means, for correcting the output thereof with respect to said second parameter and coupling said corrected output to said eighth means. 

1. An automatic control system for a distributed, controlled object which moves between an input and an output of a process, comprising: an initial-value detector for a conTrolled variable of the controlled object; a function generator to which the initialvalue of the controlled variable from said detector is applied for generating a function prescribing changes-versus-time in said controlled variable; a first analog shift register for storing a functional output of said function generator; a second analog shift register for accumulating a moving period of time of said controlled system at every movement thereof by a unit distance; a timer for generating at every movement of said controlled system a shift signal for successively shifting the contents of each analog storage element of both said registers to the adjoining element and a signal representing said moving period of time; sampling devices for taking out the contents of said each element of both said registers; a device for calculating a manipulated-variable density from said functional output and the accumulated period of time taken out by said sampling devices; an analog memory; a distributor for successively distributing said manipulated-variable density to said each analog storage element of said analog memory in synchronism with said sampling devices; and manipulating means for successively supplying said manipulatedvariable density from said memory to said controlled object, said manipulating means having a plurality of manipulators which are arranged in a manner to be distributed along said controlled object.
 2. An automatic control system according to claim 1, further comprising a detector for detecting a final value of said controlled variable; means to calculate a correcting ratio for said manipulated-variable density in conformity with a deviation between said final value and a reference value; means to multiply said correcting ratio by said manipulated-variable density; and means to supply the multiplying output from said multiplying means to said distributor.
 3. An automatic control system for controlling the characteristics of an object during a process performed on said object, through which said object passes through a processing means, comprising: first means, coupled to said object at its input to said processing means, for detecting a first parameter to be employed as a control variable for controlling said characteristics; second means, responsive to said first means, for generating a function of said control variable with respect to time and producing a signal representative of said function; third means, responsive to the rate of the entry of said object into said processing means, for generating a first timing signal representative of each increment of movement of said object into said processing means and a second timing signal representative of the time period which has elapsed from the initial entry of said object into said processing means; fourth means, responsive to said function representative signal and said first timing signal, for sequentially storing portions of said function signal as they are produced and as said object moves through said processing means; fifth means, resonsive to said first and second timing signals, for storing said second timing signals and for generating a signal representative of a lapse of time from the initial movement of said object into said processing means; sixth means, responsive to the output of said fourth and fifth means, for sampling the outputs thereof for each of said increments of movement of said object through said processing means; seventh means, responsive to said sixth means, for generating a characteristic control signal, for each of said sample outputs of said fourth and fifth means, said characteristic control signal being dependent upon the changes in said control variable; and eighth means, responsive to the characteristic control signal output of said seventh means, for applying at least one input to said object passing through said processing means, so as to control the characteristics of said object in accordance with saiD characteristic control signal.
 4. A system according to claim 3, wherein said eighth means comprises an anlog memory to which the output of said seventh means is coupled, a plurality of distributors for receiving the output of said memory and generating a plurality of manipulating signals; and a plurality of manipulating means, for receiving said manipulating signals and controlling the characteristics of said object in response thereto.
 5. A system according to claim 4, wherein said fourth and fifth means each comprises a shift register for shifting the inputs thereto in response to said first timing signal.
 6. A system according to claim 5, further including ninth means, coupled to said object, for detecting a second parameter to be employed as a correcting variable, and responsive to the output of said seventh means, for correcting the output thereof with respect to said second parameter and coupling said corrected output to said eighth means.
 7. A system according to claim 4, wherein said seventh means comprises a predetermined function generator, receiving the output of said fifth means, for generating a function of the output thereof, a first multiplier for multiplying the output of said predetermined function generator by the output of said fourth means, a second multiplier, for multiplying the output of said first multiplier by a signal representative of a prescribed parameter of said object passing through said processing means, an operational amplifier connected to the output of said first multiplier and a function generator for feeding back the output of said operational amplifier to the input thereof, a divider circuit for dividing the output of said second multiplier by the output of said operational amplifier, a comparator circuit, for comparing the output of said operational amplifier with a threshold level, and a switching circuit, for supplying the output of said divider circuit to said eighth means in response to the output of said comparator circuit.
 8. A system according to claim 4, wherein said third means comprises a first integrator circuit for integrating a signal representative of the rate of entry of said object into said processing means, a comparator circuit for comparing the output of said first integrator with a preset rate level and generating said first timing signal as a result of said comparison, a series delay circuit for delaying said first timing signal, a second integrator, responsive to an input voltage, for integrating said voltage in accordance with the output of series delay circuit.
 9. A system according to claim 8, wherein said seventh means comprises a predetermined function generator, receiving the output of said fifth means, for generating a function of the output thereof, a first multiplier for multiplying the output of said predetermined function generator by the output of said fourth means, a second multiplier, for multiplying the output of said first multiplier by a signal representative of a prescribed parameter of said object passing through said processing means, an operational amplifier connected to the output of said first multiplier and a function generator for feeding back the output of said operational amplifier to the input thereof, a divider circuit for dividing the output of said second mulitplier by the output of said operational amplifier, a comparator circuit, for comparing the output of said operational amplifier with a threshold level, and a switching circuit, for supplying the output of said divider circuit to said eighth means in response to the output of said comparator circuit.
 10. A system according to claim 9, further including ninth means, coupled to said object, for detecting a second parameter to be employed as a correcting variable, and responsive to the output of said seventh means, for correcting the output thereof with respect to said second parameter and coupling said corrected output to said eighth means.
 11. A system according to claim 10, wherein said fourth and fifth means each comprises a shift register for shifting the inputs thereto in response to said first timing signal and wherein said object comprises a slab to be cooled during a continuous casting process carried out by said processing means on said slab, said first parameter corresponds to the temperature of said slab, said prescribed parameter corresponds to the thickness of said slab, said threshold level corresponds to a threshold temperature level, said predetermined function comprises an exponential function, and said manipulating means comprises a plurality of cooling elements for cooling said slab.
 12. A system according to claim 11, wherein said ninth means comprises a winding temperature detector, for generating a signal representative of the winding temperature for said slab, a correcting device responsive to the winding temperature signal and to said threshold temperature for generating an error signal representative of the difference therebetween, and a multiplier for multiplying said error signal by the output of said seventh means so as to provide a corrected characteristic control signal to said manipulating means.
 13. A system according to claim 12, wherein said cooling means comprises a plurality of spray nozzles distributed along said object in accordance with spaces of incremental movement thereof through said processing means.
 14. A system according to claim 4, wherein said fourth and fifth means comprise a plurality of parallel-arranged shift registers, corresponding to the number of surfaces of said object to be manipulated, and wherein said seventh means comprises an adder circuit for adding the incremental outputs of said shift registers and a function generator for generating a control output in response to the sum of said incremental outputs of said shift registers in accordance with a prescribed function, a comparator circuit for comparing the output of said function generator with a threshold level, and a switching circuit for supplying the output of said function generator to said eighth means in response to the output of said comparator.
 15. A system according to claim 14, wherein said third means comprises a first integrator circuit for integrating a signal representative of the rate of entry of said object into said processing means, a comparator circuit for comparing the output of said first integrator with a preset rate level and generating said first timing signal as a result of said comparison, a series delay circuit for delaying said first timing signal, a second integrator, responsive to an input voltage, for integrating said voltage in accordance with the output of series delay circuit.
 16. A system according to claim 15, further including ninth means, coupled to said object, for detecting a second parameter to be employed as a correcting variable, and responsive to the output of said seventh means, for correcting the output thereof with respect to said second parameter and coupling said corrected output to said eighth means. 